Messaging stamp authority

ABSTRACT

Electronic messages may be processed using a stamp authority by receiving an electronic message, identifying a stamp associated the message, determining if the stamp is valid, and, if the stamp is determined to be valid, distinguishing the message from messages with which a valid stamp is not identified.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/401,965, filed Mar. 11, 2009 (now U.S. Pat. No. 8,015,607), which isa continuation of U.S. application Ser. No. 10/976,180, filed Oct. 29,2004 (now U.S. Pat. No. 7,519,559), which claims priority from U.S.Provisional Application No. 60/515,420, filed Oct. 30, 2003. The entirecontent of the prior applications is expressly incorporated herein byreference.

TECHNICAL FIELD

This disclosure relates to electronic messaging.

BACKGROUND

Pervasive communications networks are being used to exchangeever-increasing numbers of communications. These communications mayinclude electronic mail messages and instant messages.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an exemplary communications systemconfigured to exchange electronic mail messages using a stamp authority.

FIG. 2 is a flow chart illustrating an exemplary process by which astamp authority may be used to process an electronic mail message.

DETAILED DESCRIPTION

The low cost of exchanging electronic mail messages allows anInternet-based messaging system to easily exchange large numbers ofmessages to large numbers of users. The ability to send large numbers ofmessages at a low cost is used by marketers and others to sendunsolicited and/or unwanted electronic mail messages (e.g., SPAM). Manyusers receive a tremendous amount of SPAM. In fact, a user often mayreceive so much SPAM that that a user is required to dedicatesignificant amounts of time deleting the SPAM in order to manage theuser's ‘inbox.’ When barraged by SPAM, users therefore often experiencefrustration and otherwise perceive a poor user experience. The poor userexperience may lead a user to frequently change Internet ServiceProviders (ISPs) and/or online identities (e.g., screen names orelectronic mail addresses), and/or to reduce reliance upon electronicmail messaging.

The above and other issues may be avoided by reducing the volume ofunwanted electronic mail messages using a stamp authority designed toimpose a transaction cost to be borne by senders of electronic mailmessages. One implementation of the stamp authority includes a receivinghost that rejects or distinguishes received electronic mail messagesthat do not include a valid stamp. Thus, a transmitting party isincentivized to include a stamp with its electronic mail messages, thusensuring that the receiving host will process its electronic mailmessages and make them accessible to a destination client. The stampauthority effectively increases the transaction cost associated witheffectively sending an electronic mail message, leading to a decrease inthe volume of SPAM. Transmitting parties may continue to send electronicmail messages without stamps, but the receiving host may reject orotherwise distinguish/label/characterize unstamped electronic mailmessages.

A stamp authority may limit (e.g., rate limit or volume limit) a numberof stamps allocated to a party seeking to send electronic mail messages(e.g., a transmitting client). Thereafter, the party seeking to send anelectronic mail message may associate a stamp with each message or eachgroup of messages. For example, stamp identification information may beappended to the header of the electronic mail message. A host receivingthe electronic mail message may receive the electronic mail message andidentify a stamp associated with the electronic mail message. Thereceiving host determines if the stamp is valid, for example, by pollinga stamp authority. When the stamp is valid, the electronic mail messageis made available in a user's inbox. When the stamp is invalid or when astamp is not included in an electronic mail message, the electronic mailmessage may be rejected, or otherwise visually or logicallydistinguished from “stamped” messages (e.g., the unstamped message maybe placed in a folder for messages that are unstamped and may includeSPAM).

FIG. 1 illustrates an exemplary block diagram of a communications system100 configured to exchange electronic mail messages using a stampauthority. In particular, a transmitting client 110 may generateelectronic mail messages that are sent by the transmitting host 120. Theelectronic mail messages may be associated with stamps issued orregulated by the stamp authority 140. The transmitting host 120 isconfigured to exchange the electronic mail messages across the network130 with the receiving host 150. The receiving host 150 is configured toprocess and receive electronic mail messages using the stamp authority140 so that the receiving client 160 may receive the electronic mailmessages.

Generally, each of the systems shown in communications system 100, suchas the transmitting client 110, the transmitting host 120, the stampauthority 140, the receiving host 150, and the receiving client 160 maybe implemented by a computer system configured to execute instructionsin a predetermined manner.

Each of these systems may be implemented by, for example, ageneral-purpose computer capable of responding to and executinginstructions in a defined manner, a personal computer, a special-purposecomputer, a workstation, a server, a device, a component, otherequipment or some combination thereof capable of responding to andexecuting instructions. These systems may be structured and arranged toreceive instructions from, for example, a software application, aprogram, a piece of code, a device, a computer, a computer system, or acombination thereof, which independently or collectively directoperations, as described herein. The instructions may be embodiedpermanently or temporarily in any type of machine, component, equipment,storage medium, or propagated signal that is capable of being deliveredto these systems.

The transmitting client 110 includes a device configured to allow a userto generate an electronic mail message. The transmitting client 110 mayinclude one or more messaging applications that allow a user to operatean electronic mailbox used to administer a system for sending andreceiving electronic mail messages. Examples of the messagingapplications may include a messaging application integrated into anonline service provider client such as the AOL client. Other examples ofthe messaging application may include a web browser configured to enableaccess to an electronic mailbox accessible through a web server, amessaging application (e.g., Microsoft Outlook), or a server (e.g., anExchange server).

The messaging application may include a stamp agent configured toassociate a stamp with electronic mail messages. For example, themessaging application may include an “insert stamp” button in amessaging graphical user interface (GUI). When the transmitting client110 receives an insert stamp instruction (e.g., when an “insert stamp”button is pressed), a stamp transaction may be executed. For example, astamp may be associated with the electronic mail message. In oneimplementation, a stamp counter indicating a number of electronic mailmessages that may be exchanged is decremented each time a message issent. In another example, the transmitting client 110 may initiate atransaction that assesses a financial cost against a user account eachtime a message is sent.

A user of the messaging application on the transmitting client 110 neednot be aware that a stamp has been included, or even whether a stampsystem is being used. For example, the messaging application mayseamlessly interface with a stamp authority 140 to associate a stampwith an electronic mail message if a stamp is available.

The transmitting host 120 includes a messaging device configured toreceive instructions to transmit electronic mail messages from atransmitting client 110, and to transmit an electronic mail message asspecified by the transmitting host 120. For example, the transmittinghost 120 may receive a message from the transmitting client 110generated in a messaging application and transmit the message using thenetwork 130 to a receiving host 150 using SMTP (“Simple Mail TransferProtocol”) packets.

The transmitting host 120 may be configured to associate a stamp with anelectronic mail message. In one implementation, the transmitting host120 is configured to retrieve a stamp identifier from the stampauthority 140 and to associate the stamp identifier with the electronicmail message. In another implementation, the transmitting host 120 isconfigured to upload information related to the electronic mail messageto the stamp authority 140 so that the receiving host 150 may referencethe uploaded information in determining if the stamp for a receivedelectronic mail message is valid.

The network 130 includes hardware and/or software capable of enablingdirect or indirect communications between the transmitting host 120, thestamp authority 140, and the receiving host 150. As such, the network120 may include a direct link between these systems, or it may includeone or more networks or subnetworks between them (not shown). Eachnetwork or subnetwork may include, for example, a wired or wireless datapathway capable of carrying and receiving data. Examples of the networkinclude the Internet, the World Wide Web, a WAN (“Wide Area Network”), aLAN (“Local Area Network”), analog or digital wired and wirelesstelephone networks, radio, television, cable, satellite, and/or anyother delivery mechanism for carrying data.

The stamp authority 140 includes a device configured to generate, enableaccess to, associate, and validate one or more stamps used in exchangingelectronic mail messages. The stamp authority 140 may enable atransmitting client 110 and/or the transmitting host 120 to associate astamp with an electronic mail message that will be sent. In oneimplementation, the stamp authority 140 is configured to associate astamp using information related to the electronic mail message, theidentity of the user transmitting the electronic mail message (e.g.,legal name, screen name, electronic mail address, or domain name of thetransmitting host), the identity of one or more intended recipients, orthe identity of one or more organizations associated with thetransmitting client 110. There may be competing but interoperable stampauthorities that exchange information to allow electronic mail messagesassociated with stamps from the different stamp authorities to beexchanged.

The stamp authority 140 may be configured to associate a stamp in asecure manner. For example, the stamp may be encrypted using a publickey system that limits the ability of the stamp to be read to thosestamp authorities possessing the related private key.

The stamp authority 140 may be configured to maintain a stamp accountingsystem that tracks how a stamp has been used. For example, the stampauthority 140 may maintain a list of user identities or e-mail serversor domains with which the stamp authority has a relationship. The stampauthority 140 may include a meter that tracks the usage per useridentity. The meter may work in conjunction with usage restrictions thatregulate how the stamp authority may provide stamp services in supportof the user identity. For example, a user identity may receive a dailyallotment of stamps (e.g., five stamps) enabling an electronic mailmessage account associated with the user identity to send up to thedaily allotment of “stamped” electronic mail messages. When the dailyallotment has been exhausted, the messaging application in the stampauthority 140 may be configured to allow the user identity to acquireadditional stamps. For example, the user identity may purchaseadditional stamps, or to receive additional stamps given by another useridentity. In another example, the stamp authority 140 may generate aninterrogation request for the transmitting host 120 to analyze theprofile of the electronic mail messages sent by the user identity. Ifthe profile reveals that the electronic mail messages are not likely tobe SPAM, the stamp authority 140 may provide additional stamps.

The stamp authority 140 may provide stamp services for an organizationsuch as an online service provider or a company. The stamp authority 140may be configured to allocate a limited number of stamps across multipleuser identities supported by the stamp authority. Thus, a company may beallocated a specified number of stamps per month. A first user may beallowed more than their proportional share of stamps so long as thecompany has stamps available.

The stamp authority 140 may form part of a hierarchical stamp authoritystructure or may be operated in a distributed stamp authorityenvironment. In a hierarchical stamp authority structure, a stampauthority may be configured to provide stamp authority services for alimited portion of the organization. A “junior” stamp authority mayanswer stamp authority requests received from a “senior” stampauthority. The senior stamp authority may be configured to act as astamp authority 140 with respect to external systems. To validate astamp, the senior stamp authority receives the request and routes thevalidation request “downwards” to the appropriate junior stampauthority. The junior stamp authority then responds to the request andreports the result to the senior stamp authority, which in turn respondsto the request.

In a distributed stamp authority environment, different and independentstamp authorities may be configured to issue stamps to subscriber useridentities and/or organizations. When an electronic mail message isexchanged with a receiving host 150 using a different stamp authority, afirst stamp authority used by the receiving host 150 may interface witha second stamp authority used by the transmitting host 120. In oneimplementation, the first stamp authority is configured to query thesecond stamp authority to determine if the stamp is valid. In a secondimplementation, the first stamp authority is configured to maintain abalance of stamp transactions. For example, the first stamp authoritymay be configured to track the number of stamp transactions that havebeen processed for other stamp authorities and the number of stamptransactions that other stamp authorities have provided on behalf of thefirst stamp authority. In the event that an imbalance is maintained overan extended period of time, the first stamp authority may be configuredto settle the balance as a financial transaction. When the stampservices have been provided on behalf of the first stamp authority, thefirst stamp authority may reimburse the other stamp authorities. Thefirst stamp authority may receive credits for the stamp servicesprovided for other stamp authorities.

The receiving host 150 may include an electronic mail messaging systemconfigured to receive electronic mail messages from a transmitting host120. The receiving host 150 then may store the received electronic mailmessages in an inbox or file system accessible to the receiving client160.

The receiving host 150 may be configured to interface with a stampauthority 140 in deciding whether to receive an electronic mail message.The receiving host 150 may be configured to identify a stamp associatedwith an electronic mail message and poll the stamp authority 140 todetermine if the stamp is valid. The receiving host 150 then may beconfigured to process electronic mail messages determined to be valid,while rejecting electronic mail messages determined to be invalid.

The receiving client 160 may include a device used to manage andadminister an electronic mailbox used to send and receive electronicmail messages. The receiving client 160 may include the electronic mailmessaging applications described previously with respect to thetransmitting client 110. In fact, the transmitting client 110 and thereceiving client 160 may include identical or different electronic mailmessaging software. However, the receiving client 160 may receiveelectronic mail messages using a different feature set than the featureset used in transmitting an electronic mail message. For example, thereceiving client 160 may be used to administer an electronic mailmessaging system with two different inboxes. One of the inboxes mayinclude electronic mail messages associated with valid stamps. The otherinbox may include electronic mail messages not associated with validstamps, which may include messages associated with invalid stamps orelectronic mail messages not associated with a stamp.

The receiving client 160 may be used to specify preferences in receivingelectronic mail messages. Thus, the receiving client 160 may beconfigured to reject (not store or process) any electronic mail messagesunless the user administering the receiving client 160 has previouslytransmitted an electronic mail message to the party sending theunstamped electronic mail message.

Referring to FIG. 2, a flow chart 200 illustrates an exemplary processby which a stamp authority may be used to process an electronic mailmessage. Particular components described with respect to FIG. 1 mayperform the process 200. However, similar methodologies may be appliedin other implementations where different components are used to definethe structure of the system, or where the functionality is distributeddifferently among the components shown by FIG. 1.

Initially, a transmitting client 201 transmits an electronic mailmessage (206). For example, the transmitting client 201 may use anelectronic mail messaging application to generate a message window, usean address book to specify a recipient, and click a ‘send message’button to transmit the electronic mail message.

A transmitting host 202 receives the electronic mail message (210). Thetransmitting host 202 also receives a request to associate a stamp withthe electronic mail message (215). Receiving the request does notrequire that a user select an “insert stamp” button that generates anautomated request. In response to the request, the transmitting host maypoll the stamp authority 140 to determine if a stamp may be associatedwith the electronic mail message.

The transmitting host 202 determines the identity associated with a usergenerating the message for transmission (220) and the stamp availabilityfor the identity (225). For example, the transmitting host 202 may usethe sending address for an electronic mail message and may communicatewith a stamp authority 203 to determine whether the account associatedwith the sending address is allowed to associate stamps with anelectronic mail message. In one example, the stamp authority 203determines whether a counter tracking the number of electronic mailmessages that may be exchanged indicates that the identity has stampsavailable to use. In another example, the stamp authority 203 metersstamps based on the amount of the content exchanged in the electronicmail message. Thus, an identity may be allowed to send a specifiedamount of content (as measured in megabytes), irrespective of the numberof messages across which the content is distributed. Thus, an electronicmail message that consumes more memory (e.g., a video file generallyconsumes more memory than a plain text message) would reduce the amountof messages the identity may send.

The stamp authority may meter the content using a combination of themessage count and file size considerations. For example, an identity maybe allowed to transmit a specified number of electronic mail messagesper period of time, where the electronic mail messages are less than apredetermined size. Additional stamps or costs may be incurred if theidentity is transmitting a larger amount of content in the electronicmail message. In one example, the number of stamps available to theidentity may be reduced based on the size of a message sent. In anotherexample, the identity incurs additional financial costs to process theelectronic mail message with the larger amount of content.

When there is a stamp available (230), a stamp is associated with theelectronic mail message (235). In one example, associating the stampwith the electronic mail message includes modifying or appending stampinformation into the electronic mail message. In another example,associating the stamp with the electronic mail message records a messageidentifier at the stamp authority 203. Recording the message identifiermay include recording an indication of a stamp that was associated, amessage number or hash, the identity of the addressees, the time anddate of the electronic mail message, and/or other information used toidentify electronic mail message.

With or without an associated stamp, the transmitting host 202 transmitsthe electronic mail message (240) to a receiving host 204, whichreceives the electronic mail message (245). The receiving host 204determines if there is a stamp associated with the electronic mailmessage (250).

If there is not a stamp associated with the electronic mail message, thereceiving host 204 processes the electronic mail message as an unstampedelectronic mail message (255). Processing the electronic mail message asan unstamped electronic mail message may include rejecting theelectronic mail message (280), storing the electronic mail message as anunstamped folder (not shown), or performing additional processing tobetter determine if the electronic mail message is unsolicited (notshown). Generally, an electronic mail message is unsolicited if there isno prior relationship between the transmitting user and the receivinguser. Rejecting the electronic mail message may include transmitting anelectronic mail message in reply indicating that the receiving host 204,a receiving client 205, or the receiving user does not accept unstampedelectronic mail messages. The response messages may include a codesegment (e.g., an HTML link) allowing a stamp to be associated in aretransmission, or allowing the transmitting user to purchase a stamp.

If a stamp is associated with the electronic mail message, it isidentified (260). In one example, identifying a stamp associated withthe electronic mail message includes reading a stamp included in orappended to the electronic mail message. The stamp may include a labelused to identify a transaction on the stamp authority 203. The label maybe used to retrieve additional information. In another example, thestamp is not included in or appended to an electronic mail message.Instead, the receiving host 204 may reference a message number or atransmitting address used to transmit both stamped and unstampedelectronic mail messages to access the stamp stored on a stamp authority140. The message number may be used to retrieve a stamp used to transmitthe electronic mail message.

The receiving host 204 determines if the stamp is valid (265).Determining if the stamp is valid generally includes determining if anaccredited stamp was used and consumed in transmitting the electronicmail message. Determining if the stamp is valid may include determiningif the stamp was previously used, determining if an accredited authorityissued the stamp, determining that adequate stamp resources wereexpended to transmit the message (e.g., to support larger file sizes),determining that the transmitting party had adequate stamps to transmitthe electronic mail message, and/or determining that fraud was not usedin associating a stamp and sending the electronic mail message.

When the stamp is deemed valid (265), the receiving host 204 places theelectronic mail message in a stamp-related folder in an inbox (270). Thereceiving client 205 then may receive the electronic mail message (275).When the stamp is invalid, the electronic mail message may be rejected(280).

Although determining the stamp validity is shown as being performed bythe receiving host 204, determining the stamp validity also may beperformed by other devices, such as the stamp authority 203 or thereceiving client 205. Furthermore, although flow chart 200 illustratesthe transmitting host 202 associating a stamp with the electronic mailmessages, the stamp may be associated by other devices (e.g., thetransmitting client 201) and in other manners (e.g., as the message isbeing transmitted from the transmitting client 201).

Moreover, other implementations are within the scope of the followingclaims. For example, the stamps may be used per recipient or per message(where a message includes multiple recipients). And, although thesystems and operations were described with respect to electronic mailmessages, other messaging systems and operations may be used. Forexample, a stamp authority may be used in exchanging instant messages,wireless telephone messages (e.g., Short Message Service (SMS), MMS(Multimedia Message Service)), flash messages, or other messagingformats.

There may be more than one type of stamp. In addition to varying thetype of stamp with the type or size of content exchanged, the stamp typealso may be varied to offer tiered or differentiated services. Forexample, a first stamp type may indicate that reimbursement takes placeimmediately upon processing the electronic mail message while a secondstamp type indicates that reimbursement takes place after a balance ofpayments has been determined to account for a creditor/debtor statusbased on the aggregate of messages exchanged.

Other types of stamps may be associated with a particular stampauthority. For example, one class of stamps may be associated with atrusted provider while another class of stamps may be associated with astamp authority that is frequently used by mass e-mailers (e.g.,spammers) or with a reputation of not rigorously administering thestamping system.

The receiving host and/or receiving client may use the type of stamp indeciding whether or how to process an electronic mail message. Forexample, a receiving host may reject electronic mail messages from astamp authority that has been identified or associated with masse-mailers or issuing too many stamps. In another example, a receivingclient may route stamped electronic mail messages from disreputablestamp providers into an unstamped or SPAM folder. Other examples mayfeature different folders or triggering criteria associated with anelectronic mail message. For example, a service provider acting as astamp authority may offer three tiers of stamps. The first tier ofstamps may feature a basic level of service that allows the sentelectronic mail message to be placed in a ‘stamped’ inbox. The secondtier of stamps may offer one or more premium features. The premiumfeatures may route the electronic mail message to a higher priorityfolder, or include specific delivery options. In a first example, thespecific delivery options may be used to confirm receipt of theelectronic mail message. In a second example, the second-tier electronicmail message may be routed to an administrative assistant specified bythe recipient that will receive a copy of the electronic mail message. Athird tier of stamps may feature robust delivery options. For example,the electronic mail message may be forwarded to additional devicesassociated with the intended recipient such as a wireless phone orpager, or other electronic mail message accounts associated with theintended recipient. Thus, a transmitting user may pay a premium toforward the electronic mail message to a user who is on vacation butaccessing a special account to receive priority electronic mailmessages. In another example, rejected third tier messages are forwardedto a human operator that attempts to work with an administrator for thereceiving system to resolve delivery issues.

What is claimed is:
 1. A computer-implemented method, comprising: acomputer system, which includes one or more processors, generatingnon-display stamp information for an electronic message, the electronicmessage being sent by a sender and addressed to a recipient; thecomputer system associating the non-display stamp information with theelectronic message; the computer system receiving a request from therecipient, the request requesting a determination of whether thenon-display stamp information represents a valid stamp that isassociated with the electronic message; and the computer systemdetermining, in response to the request, whether the non-display stampinformation that is associated with the electronic message represents avalid stamp, and: if the non-display stamp information that isassociated with the electronic message does represent a valid stamp, thecomputer system sending a first type of response to the recipient, thefirst type of response indicating to the recipient that the non-displaystamp information does represent a valid stamp, the first type ofresponse causing a user interface, that is associated with the recipientand that is configured to display representations of electronic messagesreceived by the message recipient, to display a representation of theelectronic message in a first manner; and if the non-display stampinformation that is associated with the electronic message does notrepresent a valid stamp, the computer system sending a second type ofresponse to the recipient, the second type of response indicating to therecipient that the non-display stamp information does not represent avalid stamp, the second type of response causing the user interface todisplay a representation of the electronic message in a second mannerthat is visually distinct from the first manner.
 2. The method of claim1, wherein: the first type of response causes the user interface todisplay a representation of the electronic message in a first folder inthe user interface; and the second type of response causes the userinterface to display a representation of the electronic message in asecond folder in the user interface.
 3. The method of claim 2, whereinthe first folder is an inbox of the recipient and the second folder isan unsolicited message folder.
 4. The method of claim 1, wherein thenon-display stamp information is encrypted using a public key system. 5.The method of claim 1, further comprising: decrementing a stamp counterassociated with the sender.
 6. The method of claim 1, furthercomprising: imposing a financial transaction cost, borne by the sender,for generation of the non-display stamp information.
 7. The method ofclaim 1, wherein associating the non-display stamp information with theelectronic message comprises the computer system sending the non-displaystamp information to the sender for insertion into the electronicmessage.
 8. The method of claim 1, further comprising the computersystem receiving a request from the sender, the request requestinggeneration of the non-display stamp information for insertion into theelectronic message, the non-display stamp information being configuredto indicate to the recipient that the sender has paid a particular valueto obtain the non-display stamp information.
 9. A computer-readablestorage medium storing instructions that, when executed by a processor,perform operations comprising: generating non-display stamp informationfor an electronic message, the electronic message being sent by a senderand addressed to a recipient; associating the non-display stampinformation with the electronic message; receiving a request from therecipient, the request requesting a determination of whether thenon-display stamp information represents a valid stamp that isassociated with the electronic message; and determining, in response tothe request, whether the non-display stamp information that isassociated with the electronic message represents a valid stamp, and: ifthe non-display stamp information that is associated with the electronicmessage does represent a valid stamp, sending a first type of responseto the recipient, the first type of response indicating to the recipientthat the non-display stamp information does represent a valid stamp, thefirst type of response causing a user interface, that is associated withthe recipient and that is configured to display representations ofelectronic messages received by the recipient, to display arepresentation of the electronic message in a first manner; and if thenon-display stamp information that is associated with the electronicmessage does not represent a valid stamp, sending a second type ofresponse to the recipient, the second type of response indicating to therecipient that the non-display stamp information does not represent avalid stamp, the second type of response causing the user interface todisplay a representation of the electronic message in a second mannerthat is visually distinct from the first manner.
 10. Thecomputer-readable storage medium of claim 9, wherein: the first type ofresponse causes the user interface to display a representation of theelectronic message in a first folder in the user interface; and thesecond type of response causes the user interface to display arepresentation of the electronic message in a second folder in the userinterface.
 11. The computer-readable storage medium of claim 10, whereinthe first folder is an inbox of the recipient and the second folder isan unsolicited message folder.
 12. The computer-readable storage mediumof claim 9, wherein the non-display stamp information is encrypted usinga public key system.
 13. The computer-readable storage medium of claim9, the operations further comprising: decrementing a stamp counterassociated with the sender.
 14. The computer-readable storage medium ofclaim 9, the operations further comprising: imposing a financialtransaction cost, borne by the sender, for generation of the non-displaystamp information.
 15. A system comprising: at least one processor; anda computer-readable medium coupled to the at least one computer havinginstructions stored thereon which, when executed by the at least oneprocessor, cause the at least one processor to perform operationscomprising: generating non-display stamp information for an electronicmessage, the electronic message being sent by a sender and addressed toa recipient; associating the non-display stamp information with theelectronic message; receiving a request from the recipient, the requestrequesting a determination of whether the non-display stamp informationrepresents a valid stamp that is associated with the electronic message;and determining, in response to the request, whether the non-displaystamp information that is associated with the electronic messagerepresents a valid stamp, and: if the non-display stamp information thatis associated with the electronic message does represent a valid stamp,sending a first type of response to the recipient, the first type ofresponse indicating to the recipient that the non-display stampinformation does represent a valid stamp, the first type of responsecausing a user interface, that is associated with the recipient and thatis configured to display representations of electronic messages receivedby the recipient, to display a representation of the electronic messagein a first manner; and if the non-display stamp information that isassociated with the electronic message does not represent a valid stamp,sending a second type of response to the recipient, the second type ofresponse indicating to the recipient that the non-display stampinformation does not represent a valid stamp, the second type ofresponse causing the user interface to display a representation of theelectronic message in a second manner that is visually distinct from thefirst manner.
 16. The system of claim 15, wherein: the first type ofresponse causes the user interface to display a representation of theelectronic message in a first folder in the user interface; and thesecond type of response causes the user interface to display arepresentation of the electronic message in a second folder in the userinterface.
 17. The system of claim 16, wherein the first folder is aninbox of the recipient and the second folder is an unsolicited messagefolder.
 18. The system of claim 15, wherein the non-display stampinformation is encrypted using a public key system.
 19. The system ofclaim 15, the operations performed by the at least one processor furthercomprising: decrementing a stamp counter associated with the sender. 20.The system of claim 15, the operations performed by the at least oneprocessor further comprising: imposing a financial transaction cost,borne by the sender, for generation of the non-display stampinformation.